Chalcogen Bonds in Selenocysteine Seleninic Acid, a Functional GPx Constituent, and in Other Seleninic or Sulfinic Acid Derivatives

Abstract

The controlled oxidation reaction of L‐selenocystine under neutral pH conditions affords selenocysteine seleninic acid (3‐selenino‐L‐alanine) which is characterized also by means of single‐crystal X‐ray diffraction. This technique shows that selenium forms three chalcogen bonds (ChBs), one of them being outstandingly short. A survey of seleninic acid derivatives in the Cambridge Structural Database (CSD) confirms that the C−Se(=O)O− functionality tends to act as a ChB donor robust enough to systematically influence the interactional landscape in the solid. Quantum Theory of Atom in Molecules (QTAIM) analysis proves the attractive nature of the short contacts observed in crystals containing the seleninic functionality and calculation of surface molecular electrostatic potential (MEP) reveals that remarkably positive σ‐holes can frequently be found opposite to the covalent bonds at selenium. Both CSD searches and QTAIM and MEP approaches show that also the sulfinic acid moiety can function as a ChB donor, albeit less frequently than the seleninic acid one. These findings may contribute to a better understanding, at the atomic level, of the mechanism of action of the enzymes that control oxidative stress and ROS deactivation and that contain selenocysteine seleninic acid and cysteine sulfinic acid in the active site.

Osme bond: anisotropic distribution of electron density in action

“…Analogous -holes were then found on other elements of p-block of the periodic table (elements of groups 14, [2] 15, [3] and 16 [4]), and at the same time the awareness grew that also chemical interactions can be rationalized as periodic properties. The attractive interactions occurring between these positive regions and nucleophilic sites are now topics of intense research.…”

Thiazolium Salts as Chalcogen Bond Donors

“…An anisotropic electrostatic potential at the outer regions of bonded atoms is an established feature of elements of the p-block. − Recently, a similar behavior has been recognized also in bonded elements of some groups of the d-block. − Areas of depleted electron density with positive electrostatic potential are typically present on the atom surface at the extension of the covalent bonds formed with electron withdrawing groups. In general, the finding of sites of local most positive electrostatic potential (σ-holes) on the molecular surface can be assumed as a benchmark indication of the possibility that these sites form attractive interactions with nucleophilic sites in surrounding molecules …”

Engineering Te‐Containing Recognition Modules for Chalcogen Bonding: Towards Supramolecular Polymeric Materials

“…This results in two intermolecular Te⋅⋅⋅O ChBs displaying slightly different distances, with the shortest contact involving the σ ‐hole having the highest magnitude of highest V S,max potential. This crystal structure, hence, embodies one of the rare cases reported in the literature so far, [46,47] in which tetravalent chalcogen atoms self‐assemble through two Te⋅⋅⋅O ChBs, significantly shorted than the Σ r vdW of the atoms involved (average d Te⋅⋅⋅O =3.027 Å≪3.58 Å; average C−Te⋅⋅⋅O=171° – Figure 3 ,c ).…”

“…cases reported in the literature so far, [46,47] The synthetic strategy was, then, changed in favor of deprotonating amide 10, followed by a metalhalogen exchange (MHE) using an organometallic species, eventually adding the tellurium source to lead to the formation of Ebs-Te (Scheme S3). By using organolithium intermediates, as well as cuprate species, for the MHE step did not favor the formation of Te-containing species.…”